The majority of machine housings possess housing parts which are designed as bearing housings for rotating or sliding bearings. The bearing housing can be an integral component of the machine housing or it may be a separate entity, for example, a bearing cover affixed to the machine housing. The bearing housing, as a rule, possesses at least one bearing seat which is connected to the housing wall of the machine by means of a bearing housing wall. Under the stress of axial and radial forces, such a bearing housing wall is deformed and has a tendency to extend itself, more or less, overstepping its original positioning. In its unstressed original condition, the said bearing housing can be, to a great extent, quite flat. From the standpoint of construction as well as strength of material, the said bearing housing frequently is made in a shell form which may be enhanced with ribs in order to improve its shape-retention and to counter vibration or to cool the bearing.
Such machine housings are installed in a multiplicity of embodiments in the industry, including transmission housings, housings for drive engines, for metal working machines and to meet requirements of various applications. For example, reference is made to the book “Zahnradgetriebe”, wherein Johannes Loomann, in his design books, Volume 26, Springer-Verlag Berlin 1970, presents an axle drive, the housing of which exhibits a bearing housing for a tapered roller bearing in which the differential cage is located in the housing of the axle drive. In this case, a bearing housing is designed as a bearing cover, and covers a mounting opening for the axle drive, while the other bearing housing is an integral component of the drive housing.
The rear axle tapered drive serves a personal passenger car, wherein the differential cage is driven by a beveled pinion. The high drive moment at the said drive pinion generates a substantial radially directed bearing force, besides axial bearing forces, when motor is in a compression mode, which stresses the bevel roller bearing in a limited circumferential area. In power-input mode, the radial force is essentially less and runs about 30% of that of the compression mode. Moreover, the radial force in the power-input mode runs offset at an angle γ in the circumferential direction, in relation to the radial force of the compression mode, which angle is generally 90°. Because of the geometrical relationships of the tapered roller bearings, besides the axial forces which the bevel drive produces, the radial stresses also generate additional axial forces which act on a circumferential area wherein radial loading finds its abutment, producing, all together, an eccentrical bearing loading which results in an unsymmetrical deformation of the bearing housing wall. This is superimposed by deformations which arise because of irregular elasticities in the housing of the bearing wall and in the contiguous wall of the machine housing.
Structures pertaining to the bearing housings, which are not optimally designed in regard to their rigidity, exhibit a relatively large displacement and tipping of the bearing seat when under stress and as a result of the elastic deformation. The disadvantages which arise therefrom are multifaceted. In the building of drives and, in fact, anywhere that toothed gears are in question, such displacements of the bearing seats result in effects on the tooth contact. Deviations from the linear disposition of the tooth faces are a result of the said displacements and, in turn, lead to structural strength and to noisy operation. In order to obviate this problem, most of the toothing has a tooth-face correction. This, however, can be an optimal solution for no more than one operational condition. This said optimal condition, on the grounds of structural strength, is mostly at the maximum loading condition. Accordingly, correction is applied for that situation and correspondingly unwanted noise occurs in the preponderantly employed partially load areas. This set of problems largely comes about at the end of a drive trains in the case of bevel gear drives. At this location, high moments are in effect reacting on toothing which are sensitive in regard to their bearing support. This is the case in drives for front driven vehicles with longitudinally constructed front motors.
The same can be said for rear driven vehicles with, again, longitudinally set motors and in the case of 4-wheel drive, as well as for direct driven axles. Problems arise not only in the toothing, but also the bearing itself will fail earlier if the displacements become too great. The tilting of the inner ring and the outer ring of the bearing as well as the axial spread of the bearing seat in the case of bevel gear bearings, all lead to smaller load handling areas and therewith to higher pressures acting on the bearings.
As the loading areas become smaller, then the axial forces act with increasing eccentricity, whereby the effect of tilting is magnified and so, in turn, with increasing deformation of the bearing housing, the geometrical stress conditions become more and more unfavorable.
By means of an increased shape-retention of the bearing housing, the running wear and tilting deformation of the bearing seat can be maintained at a lower level, however, a greater stiffness of the housing leads, in general, to greater weight. This is due to the fact the most rigid state is reached when the entire available installation space is filled with supporting material. This indicates, in any case, the worst solution to the problem which, above all, is not acceptable in the vehicle world and in no way can be justified in the manufacturing design.
In the case of most of the known solutions, a larger portion of the installed material finds its place in the walls of the bearing housing. Furthermore, stiffening and reinforcing ribs are often placed in a traditional, radial disposition about the bearing axis and are circumferentially apportioned about the bearing seat. The ribs increase, in particular, the resistance moment of the bearing housing wall and, in common with the wall, are also subjected to bending.
Thus the invention has the purpose of optimizing the bearing housing of a generic machine housing in regard to the content of material and the rigidity of the same.